Whether integrated into other devices such as cellular telephones or digital cameras, or as stand-alone devices, portable devices that play music, video, or the like, commonly referred to as portable media players or PMP's, have become ubiquitous. Perhaps best known of these PMP's is the iPod line of products distributed by Apple Computer of Cupertino, Calif. Because of its popularity, the iPod also has one of the broadest ranges of accessories that address some of the inherent limitations of the iPod and other PMP's.
One such limitation is the fact that, to improve their portability, PMP's typically do not include any external speakers. While many users listen to music or other audio from a PMP on headphones, headphones are inherently limiting because, generally, only one person can hear the audio. Thus, many users prefer to connect their PMP's to remote speaker systems, since these remote speaker systems typically allow others to listen to the audio from the PMP.
Users connect their PMP's to an external speaker system, such as a home stereo, car stereo, or portable speaker system, via either a frequency modulation (“FM”) transmitter or via a cable or direct connection. FM modulators are useful for connecting PMP's to stereo systems that are not configured to accept signals from external devices, such as car stereos or the like. Frequently, FM modulators plug into the headphone jack on the PMP (and sometimes through other connectors of the PMP such as the 30-pin connector on the iPod) and broadcast the audio signal on a traditional FM frequency at a low power level so that only devices near the PMP can receive the broadcast. The broadcast signal is received by an FM tuner in the car stereo or home stereo, which then plays the music over the associated speaker system. While such FM modulators are advantageous because they allow users to listen to PMP's on sound systems that are not configured to accept wireless input from a PMP, the FM modulators typically only broadcast on one of a few frequencies, and thus are subject to interference from other FM modulators or from local radio stations broadcasting at the same frequency or neighboring frequencies. The FM modulators also tend to introduce noise into the audio signal, and to lose some of the dynamic range of the audio signal because of limitations inherent in frequency modulation.
As a result of the limitations imposed by FM modulators, many audio enthusiasts tend to prefer to connect their PMP to remote speaker systems via a cable or by direct connection. Many cables simply have a ⅛″ stereo headset plug on one end for connecting to the headphone jack on the PMP, and either an RCA, ⅛″ stereo headset, or ¼″ phono plug on the other for connecting to the remote speaker system. Because the cables plug into the headset jack, these cables receive an amplified signal from the PMP. This means the signal is likely to contain some amplified noise. This amplified signal, including the amplified noise, is then transmitted through the cable where it is subject to the induction of additional noise. Where, as is typical, the remote speakers include an amplifier, both the induced noise and the amplified noise can be further amplified, thus resulting in relatively poor audio quality. Direct connection is achieved by attaching a PMP to a remote speaker system via a docking port and connector, such as, without limitation, the 30-pin proprietary connector used on the Apple iPod. An exemplary remote speaker system that capable of direct connection with a PMP is the inMotion IM3 made by Altec Lansing Technologies, Inc. of Milford, Pa.
While cables and direct connections offer improved audio quality compared to the use of FM modulators, cables and direct connections are inherently proximity-limiting. That is, the PMP must remain tethered to the remote speaker system while the remote speaker system is in use. Because PMP's are easily stolen and easily left behind, many users would prefer to keep their PMP on their person or in their purse, coat, backpack, or the like, rather than having to leave the PMP on a desk, in their car, or next to their home stereo, but these users would rather not resort to FM modulators and the reduced audio quality associated therewith.
What is needed is a device that allows a PMP or other device to wirelessly communicate with remote speakers that is not subject to the same limitations as the related art.